1. Field of the Invention
This invention generally relates to a coolant composition for preparation of coolants used chiefly in heat-exchange systems for internal-combustion engines. More particularly, this invention relates to a coolant composition whose phosphorus content is xe2x80x9clowxe2x80x9d.
2. Related Art
Generally glycol-based coolant compositions are blended with diluent water to prepare coolants to be used in heat-exchange systems of internal-combustion engines. Conventional glycol-based coolant compositions selectively contain metal corrosion inhibiting agents or additives such as phosphates, amines, silicates, borates and nitrites in order to inhibit corrosion of metallic parts in heat-exchange systems such as aluminum, aluminum alloy, cast iron, steel, brass, solder and copper portions, which are more or less corroded without such corrosion inhibiting additives by contacting diluent water (and/or air) existing in coolants along with the coolant compositions.
Phosphates are generally regarded as an excellent corrosion inhibitor against iron and aluminum. However, phoshates are apt to cause precipitation in coolants by chemically reacting with hard water components generally contained in diluent water, which will result in deterioration of corrosion inhibiting power of the coolants.
Accordingly, it is an object of the present invention to provide a coolant composition that is capable of providing benefits from its phosphate content without presenting defects therefrom.
Other objects of the present invention will become apparent from the description that follows hereunder.
A glycol-based coolant composition according to the present invention basically contains the following ingredients in the content ranges respectively specified in groups (A)-(D):
(A) 0.1-5.0% by weight of at least one ingredient selected from group Axe2x80x2 consisting of C6-C12 aliphatic dibasic acids and alkali metal salts thereof;
(B) 0.1-10% by weight of at least one ingredient selected from group Bxe2x80x2 consisting of alkyl benzoic acids and alkali metal salts thereof;
(C) 0.001-0.1% by weight of at least one ingredient selected from group Cxe2x80x2 consisting of strontium compounds and alkali metal salts thereof; and
(D) 0.1-0.3% by weight of at least one ingredient selected from group Dxe2x80x2 consisting of phosphoric acids and alkali metal salts thereof.
A glycol-based coolant composition of the present invention may exclude therefrom such conventional additives as silicates, amine salts, borates, nitrites and molybdates so as to suppress undesired phenomena in coolants where the coolant composition is blended, without causing negative effects from not including those conventional additives.
A glycol-based coolant composition of the present invention may contain 0.01-1.0% by weight of a triazole or triazoles and/or 0.01-1.0% by weight of thiazole or thiazoles to provide additional corrosion inhibition against metals, in particular copper.